A number of the processes in semiconductor production require introduction of particular chemical substances in an ultrapure state into the process chamber or furnace. For example, wet processes require steam and dry processes require hydrogen chloride (HCl). Both of these are typically produced by oxidation in a torch chamber which feeds the oxidation products into the processing chamber. Known torches are Pyrogenic External Torches (PET) which typically include an external ignition element, a quartz hydrogen/oxygen injector, a quartz torch chamber, a safety shield, and an electronic controller for safety interlocks and operation communications with a main computer controller. Heated streams of hydrogen and oxygen are injected via a nozzle into the torch chamber, in which they ignite, thereby producing steam. These torches may also be configured for HCl production, but they then require additional heaters to maintain HCI oxidation. Existing torches in both cases tend to produce more heat than is needed by the semiconductor processing and are subject to expensive downtime when changing the input gases or in cases of heater failure. A further disadvantage is that flow control of the oxidation products is achieved by mechanical valves, which may introduce contaminants into the gas flow being controlled, especially in the case of hot and/or chemically reactive flows as in semiconductor production.
An indication of the state of the art is the torch assembly disclosed in U.S. Pat. No. 5,257,926 issued to the same assignee as the present application, the contents of which are incorporated herein by reference.